<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    

    <script>
        var num = 10;//数字
        num = "abc";//字符串
        num = true;//boolean
        num = new Object();//对象
        document.write(num+",类型为:"+typeof(num));

        document.write("<hr/>");
        age = 20;
        age = age + 10;
        document.write(age);

        document.write("<hr/>");

        let sex = '男';
        document.write(sex);

    </script>
</body>
</html>